Exposure apparatuses for semiconductor processing are commonly used to transfer images from a reticle onto a semiconductor wafer during semiconductor processing. A typical exposure apparatus includes an illumination source, a reticle stage assembly that positions a reticle, an optical assembly, a wafer stage assembly that positions a semiconductor wafer, a measurement system, and a control system.
A common type of stage assembly includes a coarse stage, a coarse mover assembly that moves the coarse stage, a fine stage, and a fine mover assembly that moves the fine stage. With this design, the measurement system constantly monitors the position of the fine stage.
With certain stage designs, vibration and disturbances from the ground or the environment are transferred to the coarse stage and subsequently transmitted to the fine stage. This can cause errors in the positioning of the fine stage. The size of the images and features within the images transferred onto the wafer from the reticle are extremely small. As a result thereof, the precise positioning of the wafer and the reticle is critical to the manufacture of high density, semiconductor wafers.